The spectre of the “worst of all possible worlds” or of the “slumification of the planet” described by M. Davis conveys an apocalyptic representation of the future for developing cities. This shortcut is nevertheless dangerous, since it obscures the diverse reality of unplanned urban forms: precarious, unsanitary slums, unauthorised peri-urban settlements, or self-built and serviced popular districts. It is this urbanisation process – through the occupation of land, the construction of housing, the progressive provision of access to electricity, water and sanitation, and ex post regularisation – that enabled the emergence of cities in Europe, and now concerns more than a third of all urban dwellers throughout the world. The fact that these urban areas emerge in an autonomous, incremental manner does not make them just vast paralysed or chaotic slums.
It is traditionally accepted that cities cannot function without planning, yet for the last 50 years, this planning has failed to steer urbanisation in the countries of the South, where almost a billion people are living in unplanned districts (according to UN-Habitat figures). Moreover, people, service providers and NGOs are also building cities every day, with other resources, tools and know-how than those used by urban planners. In view of demographic pressure and the limited capacities of the public authorities, ignoring or suppressing these unplanned dynamics proves to be not only futile, but also counter-productive. Conversely, supporting them facilitates urban regeneration, helps to gradually minimise and prevent unsafe and unsanitary housing, and enables the coordination of resources and stakeholders. There are some innovative solutions and approaches in three key areas of urban action. These show the potential of autonomous urbanisation and the important role the public authorities can play in achieving this urbanisation on a large scale.
- The social production of housing, or self-production, has proved its worth over the last 50 years, and can be encouraged by programmes to reserve land, to simplify building standards, and to secure collective occupation independently of the distribution of individual land titles.
- The provision of basic services by operators is based on technical and commercial innovations adapted to suit users. Their wider application can be facilitated by adjusting technical standards and preserving road networks for the installation of equipment, either ex ante or ex post..
- The municipal authorities can increasingly benefit from digital tools to find out about unplanned districts, to streamline management procedures, to renew relations between the public and the authorities, and to thereby ensure more informed decision-making.
In order to contribute to sustainable urban development as a whole, these tools require a supportive policy framework. The reality principle demands acceptance that autonomous urbanisation is here for the long term, and calls for a pragmatic review of the tools for urban action. Far more than through urban planning, cities are built using other technical and institutional tools. Research has already revealed some of these, which could provide viable alternatives to urban planning: policies and funding for self-construction; the issuance of temporary or intermediate property documents that are independent of land ownership status; the consolidation of road networks and districts through and around electricity or sanitation networks; the creation of open source maps and addressing systems to provide a better understanding of urban dynamics, etc. These less expensive, more flexible and accessible solutions for the local authorities already exist, but are often ignored or disdained by them. If they are to be promoted and appropriated by urban experts, policy makers and technicians, their outlooks and professional practices will need to change. At the local level, this implies abandoning the classical ideal of the modern city that is controlled and planned in favour of acceptance of popular urbanisation and recognition of other ways of building cities, focusing efforts on road networks and public spaces to improve social links, the quality of the urban environment and access to services, and sharing power and responsibilities with third party stakeholders. Over and above the issue of the investment required, this means developing a vision of the incremental extension of urbanisation in the long term, and of the human and institutional resources needed to achieve this. At the global level, further to the adoption of the Sustainable Development Goals and the New Urban Agenda, promoting new conceptual and operational frameworks is a must for meeting these commitments. However, the specific means of doing so are still unclear. Imagining new ways of building cities first implies moving away from business as usual; in other words, putting conventional planning aside. Moreover, the scope and potential of autonomous urbanisation in terms of contributing to sustainable urban development remain largely underestimated. Finally, renewing the expertise of urban professionals and providing them with alternative visions and tools is the cornerstone of any sustainable development. This is where the community of international donors can play a key role in steering the classical vision and urban development strategies towards both greater ambition and greater realism. Research can give them new ideas for addressing urban issues, by demonstrating the reality and effectiveness of alternative approaches. Between the doomsaying of “Planet of Slums” and the romanticised idea that “slum is beautiful”, rethinking precarious districts is more a matter of pragmatism than a principled position. Contemporary research is increasingly highlighting the possibilities for a sustainable reduction in urban squalor and insecurity. Helping stakeholders to anticipate and imagine urbanisation differently now implies translating these findings into operational recommendations. Here, empiricism, more than planning theories, helps to reveal grassroots alternatives and the conditions for their success, as well as the obstacles to be overcome and on which to focus public action. Capitalising on pilot projects can encourage testing of integrated projects for urban regeneration or serviced expansion for incremental urbanisation. Finally, these solutions need to be articulated within an intellectual and strategic framework that provides a credible alternative to traditional planning. This consolidation and advocacy process is a new challenge for research, to ensure policy makers and technicians appropriate these alternatives.  Davis, M. (2006). Planet of slums. New York: Verso. [Le pire des mondes possibles. De l'explosion urbaine au bidonville global. Paris : La Découverte]  Gilbert, A. (2009). Extreme thinking about slums and slum dwellers: a critique. SAIS Review, 29(1), 35–48